Low-grade fuel is inexpensive fuel and it would be desirable to use it to fuel many types of engines, particularly, gas turbines. However, low-grade fuel contains a large amount of undesirable contaminants. A significant contaminant present in low-grade fuel is vanadium. Vanadium forms vanadium oxide, V2O5, in combustion chambers, which has a highly deleterious corrosive effect on gas turbine components. Accordingly, it is necessary to remove the vanadium from the low-grade fuel before the low-grade fuel can be used in gas turbines.
Magnesium-based compounds are often added to low-grade fuel to reduce the corrosive effect of vanadium. However, the use of magnesium as an additive results in the accumulation of ash-like deposits on interior gas turbine parts, which requires periodic shutdown and maintenance of the gas turbine to remove the deposits.
U.S. Pat. No. 4,528,100 to Zarchy discloses a two step process to decrease the vanadium content in residual oil. Residual oil is first broken down into an oil phase and an asphaltene phase by supercritical or conventional extraction. The vanadium is removed from the asphaltene phase by supercritical solvent extraction and the vanadium free asphaltene phase is then re-dissolved in the oil phase for use as a gas turbine fuel.
More efficient systems and methods that improve overall reliability and availability, are needed for removing vanadium compounds from low-grade fuel.